1. Field of the Invention
The present invention relates to an optical disc drive device and a method that reads out an RF (Radio Frequency) signal from an optical disk using an RF amplifier.
2. Related Art
Generally, a pickup or the like of an optical disk drive device has mechanical fluctuation. A recent optical disc drive device has a function to adjust a radial tilt (the shift of the point on an optical disk to which a laser beam is irradiated in the radial direction) when performing record and/or playback (reproduction) of the optical disk. However, a tangential tilt (the angle shift in the rotational direction of a position on the optical disk on which a laser beam is irradiated) is not adjusted physically and mechanically.
The tangential tilt may be a cause to distort playback data. Therefore, in order to avoid the influence of the tangential tilt, the waveform distortion of an RF signal must be corrected. If not corrected, it is necessary to design a pickup so as not to have the tangential tilt. Therefore, there is a problem that the margin of the pickup and/or pickup mechanism is small and the process yield gets worse.
JP-A No. 2006-351063 (Kokai) discloses a technique to detect the tangential tilt of the optical disk drive device. However, a technique to adjust the detected tangential tilt has never been described at all in the above publication.
In recent year, there has been increasing number of proposals of systems to secondarily adjust the tangential tilt by electric signal process. For example, one way is to introduce a PRML (Partial Response Maximum Likelihood) technique, which is generally used for HDD (Hard Disk Drive), to the optical disk drive device. However, for the PRML technique, large scale operation processing circuits such as a high speed A/D (Analog to Digital) converting circuit and a Viterbi decoding circuit are used. Therefore, a chip cost increases and consumption power also increases because the chip must operate with a high speed clock corresponding to a channel rate of input signals.